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Critter Corner: The Heart of It

Feb. 6, 2011 at 2:02 p.m.
Updated Feb. 5, 2011 at 8:06 p.m.

Tuffy, a 28-year-old male African elephant, eats food left by caretakers on a snowman at the Maryland Zoo in Baltimore. An elephant's heart beats at about 30 times a minute.

By Karalyn Jones

The heart is a mysterious thing. It is one of the most central and vitals organs in our physical bodies.

Once it starts beating after 4 weeks of development in the womb, it will never stop. Ironically, it is even located in the center of our chest, despite our feeling it on the left side - the bottom leans to the left.

You could hold it in your hands, as it is roughly the size of both your fists.

The human heart has its own electrical impulse, meaning it can keep beating, even if it is separated from the body and has enough oxygen.

And despite thoughts and emotions being the result of chemical reactions in our mind, the heart is often equated with emotions.

Aristotle began this train of thought, believing the heart interacted with the rest of the organs and thus gathered sensory information from them.

The mystery continues with the animal kingdom as well.

The largest heart belongs to the largest animal, the blue whale. Its heart is as big as a car.

But technically, a dog has the largest heart in comparison with its size.

Our heart may beat faster when we attempt a difficult task, but a python's heart actually increases in size. Pythons can almost double the size of their heart before they eat. Thankfully, they don't eat daily, but can go weeks and even months on one good meal.

Speaking of beats, the smaller the creature, the larger its heart rate seems to be.

An elephant's heart beats at 30 beats per minute, while a mouse's heart tops 700.

But perhaps all that beating wears it out, since a mouse won't live three years.

Rabbits and hamsters are close behind with 400 and 450 beats per minute, respectively.

Even though a giraffe has to pump blood up 6 feet of neck, its heart rate isn't any faster than ours. It beats gravity with the strength and size of its heart - about 25 pounds and 2 feet long.

To conserve energy, many animals can lower their heart rate to a mere few beats a minute. This process is called hibernation with mammals, brummation with reptiles and diapause with insects.

A manatee can even lower its heart rate by half when it makes a long dive.

Not all hearts are equal either. Fish have two chambers in their heart, reptiles and amphibians have three and mammals have four.

One heart isn't enough for some animals. Octopuses (technically octopi) and squid actually have three hearts. Two of them are just used for pumping blood to their gills.

But earthworms have the most - because of how their body is segmented, they are said to have five.

For more animal heart facts, join us Saturday for Jungle Love as we celebrate love in the animal kingdom. The event is free with admission and includes games, presentations, art competitions and more. You can even bring valentines for your favorite zoo animal and show them how big your heart is.

Karalyn Jones is the Texas Zoo's education curator. For more information about the zoo or upcoming events, visit or call 361-573-7681.



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